North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Seeking Comcast Contact: need to troubleshoot packet loss and/or asymmetric routing issue between Comcast & Onvoy
I've forwarded your message to the appropriate team within Comcast. - Alain. > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Craig D. Rice > Sent: Thursday, August 02, 2007 9:30 AM > To: [email protected] > Subject: Seeking Comcast Contact: need to troubleshoot packet > loss and/or asymmetric routing issue between Comcast & Onvoy > > > > For four months dozens of our users who are Comcast > subscribers have had difficulty reaching St. Olaf College's > and Carleton College's network services. > > We have worked through everything we can think of with our > Onvoy (regional > ISP) network engineers. We have isolated the problem a couple > of Comcast's IP subnets, but need a contact within Comcast to > further troubleshoot. > > The behavior in a nutshell: > > -- > > User A on Comcast Subnet B browses to www.stolaf.edu (http or > https, other web sites on-site and @carleton.edu behave the > same). Our access_log shows an initial "GET /" of our > homepage, then very slow (if any) subsequent requests (for > our stylesheet or homepage images). Ping's look fine; > traceroute's look as reasonable. Telnet's to port 80 and > other services do seem to respond, albeit very slowly. > > User A has the same problem with access @carleton.edu but can > access everything else (including other Onvoy customers) > without any trouble whatsoever. > > If User A then removes his Linksys router and connects his > computer directly to the cable modem, he acquires an IP > address in Comcast Subnet C. Then, everything works fine, > including access to www.stolaf.edu and www.carleton.edu. He > puts the Linksys router back in (which still has the IP > address in Comcast Subnet B), and the problem returns. > > The problem IP subnets are completely consistent. > > Known WORKING IP Subnets: 75.72.0.0, 24.x Known > NON-WORKING IP Subnets: 71.x, 73.x > > -- > > We have already attempted the usual troubleshooting and have > eliminated user problems, computer problems, server problems, > cable modem problems, and Linksys router problems. > Traceroutes have been somewhat inconclusive since Onvoy > blocks ICMP within its network. > > So, why just St. Olaf and Carleton services? We are on a > shared physical link from Onvoy, though on different VLANs. > Onvoy has verified everything they can (routing, packet loss, > etc.) between them and us, and I'm not sure what additional > questions I can ask of them to test. Suggestions? > > Maybe Comcast has a broken transparent proxy on part(s) of > their network? > But they have told us they have nothing like this anywhere on > their network. > > Maybe there is some asymmetric routing somewhere, though all > the investigation there has come up empty. > > A third possibility is some kind of packet loss, but there is > little if any evidence of that. > > So, we are really at a loss and seek any suggestions you all > might have. And a contact in Comcast network engineering > would be especially useful to continue our troubleshooting. > > With thanks, > Craig > -- > Craig D. Rice Associate Director of > Information Systems > [email protected] Information and Instructional > Technologies > +1 507 786-3631 St. > Olaf College > +1 507 786-3096 FAX 1510 St. > Olaf Avenue > http://www.stolaf.edu/people/cdr Northfield, MN > 55057-1097 USA >
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